I. Field of the Invention
The present invention relates to the processing of source video signals for use with high definition televisions (HDTV). More particularly, the present invention pertains to a method of converting an existing source video signal to a signal having an increased frequency rate (number of frames per second) for use with HDTV.
II. Description of the Related Art
Presently available source material like motion-picture film is recorded at a temporal rate of 24 frames/second and video source material is recorded at a rate of 30 frames/second. This temporal rate of 24 or 30 Hz is too low and causes detrimental motion artifacts during camera panning, especially with large screen viewing. In addition, the Grand Alliance High-Definition Television (GA-HDTV) system developed for the United States can provide a video rate of 60 Hz or frames per second. Thus, a frame rate-up conversion from 24/30 Hz to 60 Hz is needed for utilizing information such as motion-picture films as a high quality source for HDTV.
Motion information is necessary for a high quality frame rate conversion. Known techniques such as frame repetition or linear interpolation do not suffice for conversion of data having high spatial resolution as in the case of HDTV. Although many motion compensated video coding techniques are presently known, the motion information required for frame rate conversion is not the same as that required for video coding. High quality frame rate conversion requires motion estimation that more closely reflects the true physical motion of a moving object in a video sequence.
Recently, many motion compensated frame/field conversion techniques have also become known. Techniques such as hierarchical block matching are used to generate displacement vectors that more closely reflect the true motion of the displaced objects in a video sequence, and a motion compensated filter (spatio-temporal filter) is utilized to reconstruct the continuous spatio-temporal signal. However, since some level of aliasing is always present in the sampled or scanned video signal, perfect reconstruction of the continuous spatio-temporal signal is not always possible through the use of such a motion-compensated reconstruction filter.
In addition, these known techniques for performing motion-compensated frame/field rate conversion have in general been proposed for implementation at the receiver. As the price of a receiver is sensitive to the chip count and memory, such receiver-enabled techniques are in practice limited to using only the neighboring frames relative to the subject frame for interpolation and, thus, do not have the benefit of using other frames which are prior and subsequent in time to the subject frame.